Abstract

We characterized the electronic structure of thin films by x-ray photoemission spectroscopy. We could distinguish the photoemissionspectra among the phase , the phase , and the mixed phase regime. In the mixed phase, the surface was found to be mostly . We could observe the evolution of the electronic structure in the growthphase diagram by systematically measuring core-level photoemissionspectra. The component present in the phase may be due to charge transfer to avoid the polar catastrophe of the polar thin-film surface and/or to the oxidation of the surface.

This work was supported by a Grant-in-Aid for Scientific Research (A16204024) from the Japan Society for the Promotion of Science (JSPS) and a Grant-in-Aid for Scientific Research in Priority Areas “Invention of Anomalous Quantum Materials” from the Ministry of Education, Culture, Sports, Science and Technology. H.W. and M.T. acknowledge financial support from JSPS. Y.H. acknowledges support from QPEC, Graduate School of Engineering, University of Tokyo.